Many conventional drug delivery systems include a drug container that stores a liquid drug. The liquid drug is expelled from the drug container for delivery to a patient. Many standardized drug containers have multiple internal regions of different diameters, thereby preventing the use of a plunger to expel the stored liquid drug. As a result, complex and bulky pump systems are often used to extract the liquid drug from such drug containers. Other drug containers are specifically designed to accommodate the use of a plunger. However, when the plunger is moved forward into such a drug container from an initial resting position to expel the liquid drug, a surge of liquid drug can be provided to the patient, resulting in patient discomfort. A need therefore exists for systems that can efficiently expel a liquid drug from various different types of drug containers while minimizing any discomfort to the user and reducing cost and space requirements.